| Summary: | 碩士 === 國立臺灣大學 === 電信工程學研究所 === 89 === Injection-locked technique provides an efficient approach to generate stable high frequency signal source and finds its application in phase array. It can be used to achieve synchronous operation of a number of antenna elements, and allow for the manipulation of the phase distribution without additional phase shifting circuit. Hence, in modern microwave and millimeter-wave radar, imaging, and communication systems, the injection-locking technique has the potential to be implemented for intelligent scanning antenna design.
From Chapter 2 to Chapter 4, design and experimental results of active phase array using injection-locked oscillators are presented. Each element in the array consists of a voltage controlled oscillator with an input port for injecting the locking signal, and its output port connected to a rectangular patch radiator. In other words, an active antenna integrates the oscillator and antenna on the same substrate. The oscillator is designed using cascode circuit configuration, because it has the characteristics of high power gain and can be conveniently used with injection-locking technique. The transistors used include BFG540 and NE32684A. The phase control of each radiated wave is achieved by varying the DC bias on the transistor and a range of 180o can be acquired. From the measured results of 2- and 4-element active phase arrays, the beam scanning range can be from -32.4o to 26.4o, -28.8o to 31.2o, or -12o to 10.8o. The main beam direction is shown to have a reasonable agreement between simulation and experiment.
Since the simple structure of the active phase array using injection-locked oscillators, this approach is well suited for MMIC implementation. In Chapter 5, we design a monolithic Ka-band four-element oscillator array using TRW 0.1μm GaAs HEMT foundry. This array is designed to synchronize oscillators through using a four-way power divider. A four-element rectangular patch antenna array is then connected outside the chip for the radiation. Since the MMIC is still under fabrication, the performance test will be the future work of this study.
The active phase array using injection-locked oscillators described in this thesis may find applications in digital communication systems. The array radiation beam direction is defined by properly tuning the VCO voltage of each element, whereas the digital modulation signal is fed though all the injection-locked active antennas.
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